Rebecca Kamm: That naughty thing boys doodle

I have a question; one I've pondered intermittently for a while now, and it's this: why do young men, sometimes well into their third decade, draw cock-and-balls on things? All things? And by 'things' I mean absolutely any available surface, including friends' foreheads when the booze has shut their peepers.

Who knows how far back through history C'n'B graffiti snakes, and how many other women have pondered its universality. An example was discovered recently on Renaissance painter Paolo da San Leocadio's frescos in Spain: "The truth is that we have evolved very little,'' said Carmen Perez, head of Valencia's conservation unit.

Modern C'n'B graffiti has also made the news. In 2009, a teenage boy from Berkshire called Rory McInnes painted a 25-metre-long penis on the roof of his parents' house.

They discovered it 12-months later when notified by a helicopter pilot, by which point naughty Rory was far away on his gap year.

A year later, the Long Man of Wilmington, a famous 16th century chalk hill carving in Sussex, Engand, was gifted an enormous phallus. And the year after that, Russian political pranksters/art-group Voina graffiti'd a 213-feet-tall, 89-feet-wide C'n'B onto a security service drawbridge in St. Petersburg, winning an art prize for their efforts.

We even had a C'n'B of our very own hit the international headlines once.

Newsworthy C'n'Bs aside, enthusiasts more enamoured of the pedestrian variety can luxuriate in websites and blogs dedicated entirely to the everyday sort. ("And here is a little stumpy number which brightened a slightly drizzly walk") Because, as website Gorilla Cock points out, "No matter where you are in the world, you're never very far from a graffiti'd cock!"

The practice doesn't offend me. It confuses me. Specifically, the sheer joy that doodling a C'n'B seems to bring its artists. I want to feel the joy too! Am I missing something? Do I just not GET it? And, is the modern Christian era of sexual repression to blame? A social survey revealed most of my peers were as baffled as me. As one female friend pointed out, "Girls don't draw vaginas on the toilet walls, do they?"

Other responses: "I'm guilty of this. I don't know why." "Because if we drew vaginas it wouldn't be called 'doodling'. It'd have to be renamed 'Vagoodling'." "Because it's funny and the shock factor" "For the same reason that farts are funny. Though there may well be some Freudian homoeroticism involved that you'll never get anyone to admit to."

And: "The cock-and-balls is the naughty equivalent of a smiley. Simple to do, universally recognised. You'll note that boob doodles (boobles) get more of a look in than vagidoodles, and I think it's to do with ease of recognition. Vaginas invariably look like bird beaks, fluffy triangles or mollusks.

Ease of recognition as a motivation was a recurring theme. As my (non C'n'B-drawing, I hope) boyfriend pointed out, "Vaginas are internal" and therefore trickier to draw. But they managed it back in the day! Despite the millions of C'n'Bs dotted all over the globe and sprinkled throughout the ages, it turns out the world's oldest-known cave graffiti was actually of a vagina. Except, cartoon lady-parts (were we to bother scattering them around town; personally very low on my To-Do list) would simply be passed off as a feminist statement. Or an allusion to the miracle of birth, swirly patterns and whale music, et al.

C'n'Bs, on the other hand, mean instantaneous and mocking insult. As Galen Smith, documentarian of the phenomenon (and author of New York Dick, an anthology of graffiti C'n'Bs) points out: "Tagging a poster image with a dorky penis is delivering a sexualised insult, an implication of idiocy, and an intense disrespect mixed with buffoonery. They totally reframe the dialog."

Which is fine. Reframe away, I suppose. But just one last thing: those horrible little cartoon details that some C'n'Bs have, like blunt sprouting hairs, and veins, and drips in a rainbow shape? NOOOOOOOOO.